Hi! Sally-Anne will know much more than me about the detail of such prep. I just wanted to share two things about vocab and the value of reading and speaking.
I was raised overseas and English is not my first language; I reckon it was the sixth language I heard and maybe the fourth which I was formally taught. I have never used vocab books for myself. I initially learned English a little bit as a foreign language and then suddenly found myself in England.
Strangely, the English teacher at my semi-rural school in Kent was soon complimenting me on my vocab. What helped me was that, around that time, I started to read in a big way, pretty much anything my local mobile library brought: the Sherlock Holmes stories, the Ellery Queen Mysteries, some short stories by W. Somerset Maugham, Barbara Cartland (yes!), .... I also used to read a lot about sports. My Dad, bless him, cut a deal with me: he would let me read the sports pages at the back of his copy of The Times only after I had read and discussed an article on the front page.
My DD is now in Year 7. For a while, she did try to work through her literacy and VR books, including some recommended vocab books. But she was an insatiable reader from an early age and, I believe, what helped her most was being guided towards a range of fiction and non-fiction reading, my partner sharing their love of their own books, newspapers, magazines and lots of robust debate around the kitchen table. I believe this added invaluable context to the vocab books and made the words 'sing'. She found all her VR tests straightforward.
I hope this helps.